The proliferation of smartphones is seen as central to the rollout of the Internet of Things (IoT); with consumers carrying
around an Internet-connected computer in their pocket, it can function as the gateway to the Internet for most sensors and
accessories, as well as for controlling things like home appliances via the cloud. The importance of smartphones is part of
the reason that Bluetooth is such a popular protocol choice for IoT applications; the vast majority of smartphones already
come equipped with a Bluetooth capability. Another reason that Bluetooth is popular for sensor nodes and accessories is the
availability of an ultra-low power mode – Bluetooth Smart.

Bluetooth Smart was introduced to the Bluetooth specification with version 4.0. This new version effectively detailed two
types of Bluetooth operation: Bluetooth ‘Classic’ which is similar to previous versions in laptops and headsets,
and Bluetooth ‘Low Energy’ which is designed for ultra-low power operation in things like battery-powered sensor
nodes. V4.0 effectively separates Bluetooth compatible devices into two different types, Bluetooth Smart and Bluetooth Smart
Ready.

Bluetooth Smart devices can only operate the Bluetooth Low Energy protocol (‘Single Mode’). These are the coin-cell-powered
smartphone accessories, sensors, and other applications where ultra-low power is required. Strictly speaking, a Bluetooth
Smart qualified product must meet three requirements: incorporate Bluetooth Core Specification Version 4.0 (or higher) with
Generic Attribute (GATT)-based architecture; feature a single mode radio; and use the GATT-based architecture to enable particular
functionality of the device.

Bluetooth Smart Ready devices can operate both Classic Bluetooth and Bluetooth Low Energy (‘Dual Mode’). These
are the hubs and gateways of the IoT, the smartphones, the tablets, the PCs, the games consoles. Strictly speaking, a Bluetooth
Smart Ready qualified product must also meet three requirements: incorporate Bluetooth Core Specification Version 4.0 (or
higher) with GATT-based architecture; feature a dual mode radio (BR/EDR + Bluetooth low energy) where both radio modes may
be activated, individually or simultaneously; and provide a means by which the end user can choose to update functionality
for a Bluetooth Smart device on the Bluetooth Smart Ready device.

So, what’s the difference between Bluetooth 4.0, 4.1 and 4.2? In a nutshell, 4.1
is a software update which added the ability to coexist with LTE without interference, made the reconnection time interval
flexible and variable, which allows automatic reconnection, and improved bulk data transfer efficiency. Version
4.2 is a hardware and software update, which improves privacy and security while increasing speed, as well as allowing
IPv6 for Bluetooth via a new profile. This is a key development, since it will allow Bluetooth devices to become a part of
the Internet proper rather than being connected via a bridge or gateway, bringing IP all the way to the end node.

Bluetooth radios also come in three different classes. Class 3 devices have a range of about a metre. Class 2 devices have
a range of about 10 metres, and are typically used in portable devices. Class 1 devices, with their range of 100 metres, are
primarily used in industrial applications.

Designing-In Bluetooth Smart

With wireless connectivity becoming standard for pretty much all electronic devices as part of the IoT, a lot of electronics
design engineers are finding wireless added to their remit. However, not all engineers with expertise in embedded computing
will be experienced in wireless technology. In fact, a lot still see it as tantamount to black magic. RF designs can be extremely
challenging to execute to the required levels of interference, and there are rigorous certification processes that have to
be understood and passed before any device with wireless capability can reach the market.

That’s why many engineers are taking the easy route and choosing a ready-made, ready-certified wireless module. This
approach gets rid of the headaches of certification, which in practice are often only viable for very high volume designs.
Using a module also allows embedded engineers to concentrate on what they do best, application hardware and software.

The good news is that pre-certified Bluetooth modules are widely available and there is a huge variety.

Bluegiga has
the WT41 very long range (Class 1) Bluetooth module with an impressive 1000 metre range, for use in the industrial environment
as well as for medical and M2M applications. The module integrates a Bluetooth radio, Bluetooth v2.1 software stack and profiles.
It’s CE, FCC and IC qualified and operates over the industrial temperature range of -40 to 85°C.

Microchip’s BM77 Bluetooth v4.0 module operates Bluetooth Classic and Bluetooth Low Energy. Measuring just 22 x 12
x 2.4mm, it is suitable for home automation, LED lighting and even wearables and fitness equipment. It has radio certifications
from the Bluetooth SIG, FCC, IC, CE, Japan and KCC.

wireless sensors and fitness equipment like heart rate monitors. It has a tiny footprint – just 9 x 9.5 x 1.8mm –
and it uses just 5mA of current when transmitting or receiving in Bluetooth Low Energy mode.